A laboratory analyzes biological materials left on evidence submitted by law enforcement agencies. The DNA unit typically does a visual examination for biological stains and a chemical screening test to indicate the presence of stains. If these tests screen positive, a sample of the suspected biological stain is collected, and DNA is then extracted from the stain. Once the stain is extracted, the DNA unit will quantify the amount of DNA present in the sample. If there is sufficient human DNA present, the sample will be amplified and run on a Genetic Analyzer instrument.